Superheat control for water-tube boilers



SUPERHEAT CONTROL FOR WATER TUBE BOILERS Filed July 28, 1927 WW /wf Patented Aug. 6, 1929.

PATENT GFFICE..

HARTOLD EDGAR YARROW, OF GLASGOW, SCOTLAND.

-SUPERHEAT CONTROL FOR WATER-TUBE IBOILllR-S.

Application led July 28, 1927, Serial No. 209,096, and in Great Britain` July 2, 1926.

The object 4of this invention is to provide means for conveniently regulating the degree of superheat imparted to steam by a superheater in water tube boilers, comprising steam and water drums, so as to be able to meet changed conditions of working which would alter the superheat temperature, as, for example, the conversion of the boiler from a coal-fired to an oil-fired boiler, or conversely.

It is usual to interpose a bank of superheater tubes between two or more banks of steam generating tubes, so that it is screened, at any rate partially, from direct radiation from the furnace.

The present invention relates more particularly to the method of mounting and adjusting a sliding baille or bullies used for controlling the flow of furnace gases to the superheater, and incidentally screening the superheater tubes from direct radiation from the combustion space of the furnace.

According to the invention the adjustment of the sliding baille, or of each baille,

y is effected by means of screw-threaded rods carried by hangers fixed to the steam drum or other suitable part of the boiler plant and screwing into nuts which engage or are carried by the baille, either thc rods or the nuts being preferably operable from outside the boiler. The rods and baille are so positioned with respect to each other that those parts of the rods which are not screwed linto the nutsare screened from the furnace by the baille, the remaining portions of the rods being protected from the furnace gases by the nuts themselves which, for this purpose, are preferably in the. form of threaded sleeves, or have sleeve extensions, of any suitable heat-resisting material.

The sliding baille is interposed between the superheater tubes and a bank of steam generating `tubes which partially screens the superheater from direct radiation from the combustion space, and the arrangement is such that in one limiting position of the baille the whole of the furnace gases which traverse this bank of generating tubes passes amongst the superheater tubes and screening from direct furnace radiation is a minimum, while in the other limiting position screening from drect radiation is a maximum, and a passage or by-pass is at the same time opened to its maximum extent to permit furnace gases which traverse the bank of steam generating tubes to pass around the end of the bank of superheater tubes.

The invention will. be further described with reference to the accompanying diagrammatic drawing, in which Fig. l is a view of a. portion of a water tube boiler plant1 showing banks of steam generating and superheating tribes and provided in accordance with the invention with a baille device; and Fig. 2 is a fragmentary elevational view of the baille device in Fig. l, tbe baille being shown as consisting of two sections.

ln the drawing, A is the saturated steam drum situated above the furnace chamber l; BBB are the water drums, CCC are the banks of steam generating tubes connecting the water drun'is with the steam drums, the latter banks of tubes forming the generating heating' surface of the-boiler; l) is the superheater drum; E the bank of superheater tubes through which the steam passes and 1n which it is superheated to the required temperature.

It will be seen that the super-heating tubes in bank E are placed between two banks or nests C of steam generating tubes, the nest of steam generating tubes nearest the furnace I reducing the temperature of the gases, so that the superheater .is not liable to become overheated, and at the same time this nest of generating tubes acts as a more or less complete screen, so that the superheatei.' tubes are not exposed to the full ratiation from the furnace.

The baille for controlling the superbe-at consists of movable battle plate or plates F, which are placed between the screening bank of steam generating tubes and the superheater tubes.

The baille, which may, as shown in Fig. 2, be in two or more independently operable sections, is supported from hangers JJJ which are fixed to the steam drum or other suitable part or parts of the boiler plant, in suoli. manner that it can be translationally moved with respect to the supporting hangers, and the adjustment of the baille is effected by means of screw-threaded rods Gr carried by the fixed hangers J and nuts or threaded sleeves H. Either the screwthreaded rods or the nuts may be rotated from` outside the boiler casing. For example, each of the nuts or screw-threaded sleeves H may be rotated by means of a turn-key H1 having a slot H3 on its end portion H2 adapted to engage with a pin H4 on the sleeve H.

If the plate F be moved upwards so that its upper edge is in the position marked X in Fig. 1, then the whole of the gases from the furnace would have to pass across the bank of superheater tubes, which are also subject at the same time to the maximum radiation possible, and the superheat would be a maximum. If the baille plate F be moved so that the top edge is in some lower position, say at the point Y, then a large portion of the superheater bank would be screened from the gases and from the radiation, while at the same time a by-pass would be provided for the gases over the top of the superheater. This would have the effect of reducing the transfer of heat and the degree of superheat.

The nut H may be made of any appropriate heat-resisting material and be so formed, as by having a sleeve extension,

that it protects the portion of the screwthreaded rod Gr which projects through the lower flanged edge of the baffle F, vhich may also be of the same heat-resisting material. The portion of. the srew-threaded rod G which is above the lower edge of the baille plate F is placed behind the bafile plate, so that the rod is protected throughout its whole length from the heat of the furnace.

Having thus described the nature of the vsaidinvention and the best means I know of carrying the same into practical effect, I claim:-

l. In a Water tube boiler embodying a furnace, a steam drum above said furnace, a water drum arranged laterally of said furnace,rbanks of steam generating tubes connecting the water drum andsteam drum and past which the furnace gases pass to the ilues, and superheater tubes arranged between the banks of steam generating tubes and the flue, means arranged between the banks of steam generating tubes and superheater tubes for controlling the ilow of furnace gases past the superheater tubes, Said means comprising a baille movably mounted between the banks of steam generating tubes and superheater tubes, screw-threaded rods engaging a iixed abutment, and nuts engaging said bafile and the screw-threzuled portions of said rod.

2. In water tube boilers a sliding adjustable baille for controlling the flow oi gases to a superheater and interposed between a superheater and a bank of steam generator tubes on the furnace side of the superheater, and means for adjusting the baille, said means comprising hangers fixed to the steam drum, nuts carried by the baille, and screwthreaded rods supported by said hangers and screwing into said nuts.

3. In water tube boilers an adjustable baiile according to claim l, wherein the screw-threaded rods are located on the upper side of the baille.

4. In water tube boilers an adjustable baille according to claim l, wherein the nuts are in the form of threaded sleeves oi heatresisting material.

5. In water tube boilers an adjustable baiile according to claim 1 including hangers for supporting the screw-threaded rod and, wherein the lower ends of the hangers and of the baille are ilanged and pierced to receive the screw-threaded supporting rods.

(3. In water tube boilers an adjustable baille according to claim l, whereinthe baille is made in two or more independently operable sections.

7. In water tube boilers an adjustable baille according to claim 1, wherein the nuts are in the form of threaded sleeves adapted to cover the portions of the screw-threaded rods which project past the lower edge of the baifle.

In testimony whereof I have signed my name to this specification.

HAROLD EDGAR YARROW. 

